U.S. Pat. No. 6,096,676 mentions, among other things, catalyst precursors and catalysts comprising a Group 4 metal.
U.S. Pat. No. 6,803,433 B2 mentions, among other things, metalloenamine compounds and catalysts comprising a metal that is nickel, palladium, platinum, titanium, zirconium, hafnium, vanadium, or scandium.
U.S. Pat. No. 6,919,413 B2; U.S. Pat. No. 6,919,467 B2; and U.S. Pat. No. 7,199,255 B2 are family members that mention, among other things, catalyst precursors and catalysts comprising a metallic element of any one of Groups 1 to 15 and the lanthanide series (of the Periodic Table of the Elements disclosed in Lange's Handbook of Chemistry (McGraw Hill Handbooks, 15th edition, 1999).
Chemical industry desires new metal-ligand complexes and catalysts prepared therefrom with improved stability (e.g., towards alkyl group migration) under olefin polymerization reaction conditions (e.g., temperature). Preferably, the new catalysts would be useful for catalyzing reactions that provide new compositions of matter (e.g., new polyolefin compositions), improving reaction yields, providing alternative substrate selectivities (e.g., providing a new relative selectivity for a monomer and co-monomer in making a polyolefin copolymer), reducing manufacturing costs, improving process safety, or a combination thereof.